Power transmission belt



L. H. GILMER El AL IONER TRANSMISSION BELT Filed June 5, 1931 ATTORN EYOct. 9, 1934.

Patented Oct. 9, 1934 d POWER TRANSMISSION BELT Ludwell H. Gilmer,Philadelphia, Pa., and George Walker Gilmer, Detroit, Mich.

Application June 5, 1931, Serial No. 542,398

8 Claims. (Cl. i4-238) This invention relates to the manufacture ofFigure 6 is a cross sectional view of the core endless belts,particularly those belts suited for for the belt shown in Figure 4 afterbeing comrunning in grooved pulleys. pressed to form the belt shown inFigure 9.

rThese belts may be of the so-called v cross Figure 7 is a crosssectional view of the core section in shape, round, semiround, or of anyunit after being compressed to form a belt as 39 necessary shape toallori7 the tractive surface of shown in Figure 10. the belt to t in thegroove or pulley on which Figure 8 is a cross sectional view of theround it must operate. In the V construction the tracbelt shown inFigure 4. tive surfaces of the belt fall in planes not par- Figure 9 isa cross sectional view of a semilll allel, but at an angle each with theother. This round belt in which the core unit is shown in 65 angleshould correspond approximately with the Figure 6 is used. angle of thefaces of the grooved pulley in which Figure 10 is a cro'ss sectionalview of the V type it Operates. of belt in which the core shown inFigure 7 is Heretofore belts of the above types have been used.

made in a number of ways, some with leather, Figure 11 is a top planview of a section of com- 70 rubber or cotton of uniform structure, andmatepleted core. Tiel, throughput the CIOSS Section; Others, geri- Thereference numeral 11 designates the prierally more Satisfactory for egeneral purpose mary core of whatever form in cross section of belt.have been mede by 115e of a number of plys the belt desired, aroundwhich is built up the 2G or thicknesses or strips of Woven fabric piledone core unit l2. This cord unit is composed of the 75 0D top 0f theOther usuelly in longitudinally two groups of strands 13 and 14. Thegroup of 'Spiral ferm t0 ferm a @Ore and Supply the Chief strands 13 andthe group of strands 14 are wound tension member of the structure.Others have spirally in opposite directions. when the desired tile eOlefermed by a number of cords placed strength and diameter of belt hasbeen built up of approximately parallel with each other, Semetheoppositely wound strands a jacket of rubber 8o times e. Single cordWound spirally in the diree- 15, or similar, or suitable, composition isapplied tien 0f length 0f belt and repeatedly erellnd e around the coreunit, and the whole covered by mandrel to form a multi-cord core orchief tenan outer covering or envelope 16, which latter Sion member. All0f these COIeS are 95 e. I'Llley constitutes the tractive or wearresisting surface 3o regardless of their initial structure, surroundedof the completed belt, 85 by rubber in a semi-cured condition and thenout` The free ends 17 are secured to the core body in side of thisrubber is placed a jacket of rubberized any desired manner, fabric toform a tractive and wear resisting sur- The Core unit; may be made toconform to the face. The eempleted belt iS then VllleenZed 1111- desiredultimate shape of the completed belt, or

der pressure in a ferm t0 produce the desired it may for some purposesbe placed in the covering 90 CrOSS-Seetienel Shape. 16 and then formedin the process of enveloping The objects of our invention is to providea it in the covering 16, more iiexible, higher speed, stronger belt withWhile We have fully described the method of less internal friction, lessliable to stretch or conbuilding up the Single Core with alternate right40 tract and 2' b et more dumme and with higher and left spirally woundlayers of strands, we do 95 power transmlsson Capacity for a gwen Cross'not wish to be limited to this construction es it is ,Seoe drawing.entirely possible to construct the core by braiding l E a number oflayers of strands around the primary Figure 1 1S a' 51de elevatmn of E'belt cme emcore, such member having the same capacity for bodying ourinvention.

e 1A um of a son rima? being formed into the stress member of a belt.mgm 2 is a sld e eva l d p y Where the strands of libre are coated withrub- 1 corpgfleols'sde elevation of d tubular primary ber, the rubberwill, on application. of heat flow Core fm- Ombelt, d and vulcanize as asomewhat elastic bond `tying Figure 4 is a, Side elevation Gf a, beltembodying the individual strands together lIltOnE. SllfClel'l-ly 105 ourinvention with the ends of the two layers of yielding mass te allow thealmost imperceptible strands ready to be secured to the body of theshifting or 1re-aligning of the strands in passing belt. around thepulley. This rubber when it flows also Figure 5 is a, cross sectionalview of the core tends to combine with the primary core and the for thebelt shown in Figure 8. outer layer of cord enveloping rubber, which on110 application of heat, also -flows and ties the cord in resilientrelation to the jacket.

Where the cord unit is composed of uncoated strands of fibre it may bedipped or impregnated with the necessary coating compound, or having aprimary core of rubber, and being encased in rubber, and then surroundedby the cover 16, on

application of heat, the rubber of the primary core and the coveringrubber inside of the cover 16 will tend to flow and unite in and aroundthe strands comprising the core unit.

In the following description of the methods employed in the making ofbelts to meet the above objectives, particular attention is given to thestructure and formation of the belt core, on which all of the aboveobjectives primarily hinge. This core consists of a single endless cord.

In our invention the core is built up largely of a number of integralstrands wound spirally in layers around the central primary core. Eachlayer of these spirally wound fibres or threads is axially wound in adirection opposite to the layer preceding it.

In starting this single cord construction belt, it is necessary first todetermine the length of cord required to make a belt of the desiredlength, once this length is determined, a primary core, which may becomposed of threads or yarns, or made up of rubber or other suitablecomposition, is laid down around pulleys or form set to the properlength. On this primary core is then axially wound, in progressivespirals, layers each composed of a number of strands of fibres, eachlayer being wound in a spiral direction opposite to the preceding layeron`which it rests. These layers are continued progressively around thebelt until the cord is built up to the required diameter. T'he free endsof the strands of fibre are then secured in any desired method to thebody of the cord unit. They may be cemented with rubber gum, cement ordrawn under previously lain spirals, or stitched, or otherwise fastened.

In the above construction the strands of fibre may be coated with apreparation which in later process of manufacture may serve to insulatethe individual strands of fibre from each other and/ or insulate thesuccessive layers of strands from each other.

After the cord unit has been built up to the desired dimensions it maythen be pressed, rolled or formed into the desired final cross-sectionalshape for use as a core for the finished belt. This core may besurrounded with a jacket of a semi-cured more or less plastic and moreor less elastic composition of the nature of rubber, and then aroundthis composition may be placed a fabric or other suitable cover orenvelope to serve as a tractive or wear resisting surface.

The belt as constructed may then, under pressure in a form of desiredshape 'and dimensions, be cured to an extent necessary to allow it tomaintain the desired form in service.

Inthe foregoing construction the primary core, forming the first step inthe construction of the cord unit, if composed of strands of fibre willeasily be displaced u nder pressure and allow the cord unit to assumethe desired cross-sectional shape.

This primary core may be composed of an endless structure of semi-curedrubber or similar preparation, or it may be of rubber or other similarcomposition in tubular form. Either of these structures, on applicationof heat or pressure, or both, will allow the cord unit to assume thedesired cross-sectionalgshape.

fort to follow a straight line.

It is a fact well-known to makers and users of belts that there isconsiderable internal friction set up in a belt, in moving aroundpulleys, by compression of the inner surface of the belt and tensionwhich leads to stretch on the outer surface of the belt. In the beltmade according to our invention each successive layer, in each spiralconvolution, lies alternately on the inside and on the outside of theneutral axis of the belt. Being tightly wound, around the primary coreand the previous layers, the spiral convolutions can not stretchappreciably in their natural ef- Therefore, with a somewhat elastic bondbetween the individual strands or layers, these strands or layers areenabled to give so that compression on the surface of the cord unitbelow neutral axis helps to compensate for the tension or tendency tostretch on that surface of the cord unit which is outside of the neutralaxis.

The cord unit of the belt may, according to our invention, be built upby hand or on a suitable machine.

The words "core unit as used herein means the complete unit built uparound the primary core.

What we claim is:

1. A power transmission belt comprising an endless central primary core,of small diameter relative to the belt, extending along the central axisof the belt, and an endless cord unit composed of successive layers ofstrands, each consisting of a plurality of parallel strands, said layersbeing successively and alternately wound spirally in opposite directionsabout said core and upon each other to form a belt of suchcrosssectional shape that at least those layers lying adjacent to thecore and for a distance radially between the core and surfaces of thebelt lie concentric with relation to the core.

2. A power transmission belt comprising an endless central axial core,of small diameter relative to the belt, and an endless cord unit builtup of successive layers of strands, each consisting of a plurality ofparallel strands, successively and alternately wound spirally inopposite directions about the core and upon each other, said windingsproducing a belt of a cross-sectional shape in which at least thosewindings between the core and circumferential center of the belt arearranged concentric with said core and so that each successive layer ineach spiral convolution lies alternately on the inside and on theoutside of the neutral axis of the belt.

3. A power transmission belt comprising an endless central axial core ofsmall diameter relative to the belt, and an endless cord unit built upof successive layers of strands, each consisting of a plurality ofparallel strands successively wound spirally and alternately in oppositedirections about the central core and upon each other, said layers beingso arranged and the belt being of such shape in cross-section that atleast those windings between the core and circumferential center of thebelt are disposed concentric with said core.

4. A vulcanized power transmission belt comprising an endless centralcore of small diameter relative to the belt, and an endless cord unitbuilt up of successive layers of rubber coated strands, each consistingof a plurality of parallel strands, wound spirally successively andalternately in opposite directions about the core and upon each other,said belt being vulcanized to elastically bind the rubber components andbeing comtive to the belt, extending along the central axis of the belt,an endless cord unit composed o1' successive layers of strands, eachconsisting of a plurality of parallel strands, said layers beingsuccessively and alternately wound spirally in opposite directions aboutsaid core and upon each other to form a belt oi such cross-sectionalshape that at least those layers lying adjacent to the core and for adistance radially between the core and surfaces of the belt lieconcentric with relation to the core, a rubber jacket about the core,and a casing enclosing the jacket.

6. A power transmission belt comprising an endless central axial core ofsmall diameter relative to the belt, an endless cord unit built up ofsuccessive layers of strands, each consisting of a plurality of parallelstrands, successively and alternately wound spirally in oppositedirections about the core and upon each other, said windings producing abelt of a cross-sectional shape in which at least those windings betweenthe core and circumferential center of the belt are arranged `cncentricwith said core and so that each successive layer in each spiralconvolution lies alternately on the inside and on the outside of theneutral axis of the belt, a rubber jacket about the core, and a casingenclosing the jacket.

7. A power transmission belt comprising an endless central axial core ofsmall diameter relative to the belt, an endless cord unit built up ofsuccessive layers of rubber coated strands, each consisting of aplurality of parallel strands successively wound spirally andalternately in opposite directions about the central core and upon eachother, said layers being so arranged and the belt being of such shape incross-section that at least those windings between the core andcircumferential center of the belt are disposed concentric with saidcore, a rubber jacket about the core, the said jacket and aforesaidrubber components of the windings being elastically combined byvulcanization, and a casing enclosing the jacket.

8. A vulcanized power transmission belt comprising an' endless centralcore of small diameter relative to the beltand an endless cord unitbuilt up of successive layers of rubber coated strands, each consistingof a plurality of parallel strands, wound spirally successively andalternately in opposite directions about the core and upon each other,said belt being compressed to a predetermined cross-sectional shape suchthat at least those windings between the core and circumferential centerof the belt are arranged to lie concentric with said core, a rubberjacket about the core, the said jacket and aforesaid rubber componentsof the windings being elastically combined by vulcanization, and acasing enclosing the jacket.

LUDWELL H. GILMER. GEORGE WALKER GILMER.

